1. Field of the Invention
The invention, according to a first and a second aspect, relates to a method of transferring a web, in particular a paper or board web, preferably running over a subregion of a winding roll, to a new core.
According to a third aspect, the invention relates to a method of transferring a web, preferably running over a subregion of a winding roll, in particular a paper or board web, to a new core forming a nip with the winding roll, in particular an empty spool. At least one transverse strip is preferably formed in at least one edge region of the web by way of at least one cutting device, preferably a transverse cutting device. This device may be arranged upstream of the nip in the running direction of the web. The invention additionally relates to an apparatus for implementing such a method with at least one cutting device, preferably a transverse cutting device.
The invention additionally relates to a respective winder for implementing such methods.
2. Description of the Prior Art
Such methods of transferring a web are applied, for example, in the region of a reel-up of a machine for producing paper or board, a coating machine, a slitter-rewinder or an equivalent machine, in order to wind up the web onto a plurality of empty cores one after the other, which are also referred to as empty spools. This occurs without interrupting the production process, that is to say without stopping the paper or board machine, or in order to wind up the web onto a preferably empty core sporadically, that is to say following a break in the paper or board web or after starting up the paper or board machine.
In the process, it must be ensured that the web start produced by cutting the web is supplied to the new core, in order to form a new wound reel on the latter.
German laid-open specification DE 42 08 746 A1 discloses a method of changing spools in which a web supplied continuously to a winding roll is transferred to a new spool (empty spool) which is in contact with the winding roll.
In this case, a central part of the web, what is known as a transfer strip, is cut by two cutting apparatuses at a point which is located above the winding roll in the running direction of the web. The transfer strip is provided with an adhesive medium on the top side, that is to say on the side facing the empty spool, by means of an adhesive supply apparatus and is stuck to the surface of the empty spool. The transfer operation is completed by the movement of the two cutting devices in the direction of the respective web edge.
In this method, it is therefore assumed that the adhesive medium has the capacity of tearing through the transfer strip completely and reliably at the latest as it leaves the nip.
Unfortunately, in practice this assumption is confirmed only in the rarest cases. This has also been recognized by the inventors of the aforementioned specification and, in order to divide the transfer strip (cutting the web between the cutting lines), a separate strip dividing device was proposed. Thus, in this embodiment, the method already disclosed by U.S. Pat. No. 4,445,646 A is used to its full extent, which has been expanded by the supply of adhesive medium to the top side of the transfer strip.
In this method, the outlay on construction and the exceedingly large number of components and subassemblies are disadvantageously required. In addition, chronological synchronization and reproducibility of the individual method steps constitute an uncertainty factor in the transfer of paper webs. Furthermore, the method is absolutely unsuitable for transferring paper webs with a high tearing strength, such as plastic webs and board.
The use of adhesives for the simultaneous cutting and transfer of the transfer strip to the empty spool is also in the foreground in the method disclosed by the published PCT specification WO 97/48632 A1. In addition to the already disclosed double-sided adhesive tape or label, the use of adhesives in the form of hot-melt and the like is also proposed here.
Furthermore, not only the application of the adhesives to the top side of the web but also the application of the adhesives to the circumferential surface of the empty spool is provided. This is a further possible way of supplying adhesive, but can have a decisive influence on increasing the reliability of the method.
On the other hand, one difference with respect to the German laid-open specification DE 42 08 746 (cited above) is to be found here in the arrangement and selection of the cutting apparatuses. Here, the use of mechanical circular knives which, in practice, are associated with many disadvantages, is dispensed with, and instead a water jet is provided as the cutting medium, with which the web can be cut both upstream of and directly on the winding roll.
The restriction to cutting the web with water jet at a point at which it is already guided over a part of the winding roll and supported is not absolutely necessary for process reasons. However, since a water-jet cutting apparatus upstream of the winding roll has already been disclosed by the German laid-open specification DE 42 08 746 A1 (cited above), in particular, as column 5, line 32, this restriction is nevertheless understandable. In addition, in this method the main disadvantage is to be seen in the fact that it is absolutely unsuitable for transferring paper webs with a high tearing strength.
Another idea with regard to the cutting of the transfer strip is disclosed in European patent application EP 0 543 788 A1. Although the separate strip dividing device is arranged downstream of the nip, as opposed to the two specifications already cited, DE 42 08 746 A1 and U.S. Pat. No. 4,445,646 A, it is not arranged on the top side of the web. The severing of the transverse strip, for example, by an air jet aimed at the web and empty spool, can then be configured relatively reliably in many webs. In order to implement this, however, the contact between the winding roll and the full roll must be canceled, at least briefly, which represents a critical disadvantage in a continuous winding process. In most cases, specific winding methods are required for this purpose which, amongst other things, include center drives and elements forming substitute nips. Methods and apparatuses of this kind are described, for example, in the two European patents EP 0 483 092 B1 and EP 0 788 991 B1, the PCT published specification WO 98/52858 A1, and the German laid-open specification DE 198 07 897 A1. However, these documents necessitate higher investment and operating costs. In addition, because of their operating mechanisms, they can lead to damage to the surface of the web.
A further disadvantage of these methods is represented by the rather random transfer of the web start to the empty spool. Although blowing on with an air jet is disclosed, in truth in this case trust is placed on what is known as self-threading of the web start onto the new core. In practice, this method can be used only conditionally: webs with a high grammage or stiffness, for example, such as board, cannot be transferred at all in this way. In addition, as a result of the lack of a connection between the web start and empty spool, no clean winding start can be ensured.
Furthermore, U.S. Pat. No. 5,954,290 A also discloses an apparatus for transferring a moving paper web to a new core. In this case, provision is made that, in an edge region of the paper web, a high-strength dividing tape, whose length is a multiple of the web width, can be introduced directly into the nip in such a way that its start is connected to the new core. After that, the dividing strip is wound spirally onto the new core, simultaneously tearing through the entire web and transferring it to the new core.
Although this method, which has been known for decades and is common, in particular, in the paper industry, has been improved continuously and developed further over the course of time, until now its principal disadvantage could not be eliminated. This consists in the fact that, after the spool change, the dividing tape remaining on the surface of the core, whose thickness cannot be arbitrarily small, for process reasons, always produces pressure points in the web which lead to the production of a considerable quantity of broke in the core area of the roll, which has a highly detrimental effect on the efficiency of the overall production process. A further system-induced disadvantage of this method is to be seen in the necessity for the dividing tape to have to be introduced directly into the nip, which means that the position of the nip virtually cannot be changed. Furthermore, the dividing tape used for tearing the web represents a great danger of injury and fatality, and not just potentially, to the operating personnel. In addition, the question of environmentally suitable disposal of the dividing tape, used as a disposable product, is increasingly gaining importance.
Still further methods and apparatuses for transferring a moving web are known from various other publications, but are all afflicted with more or less severe disadvantages.
For example, U.S. Pat. No. 4,444,362 A discloses a method in which, in principle, there is no transfer strip at all, since the web start is already formed completely upstream of the winding roll by means of the transverse cutting devices.
As a result of arranging the transverse cutting devices downstream of the nip, as compared with this, a far more reliable method is produced, which likewise dispenses with the formation of transfer strips. However, this method, disclosed by European patent application EP 0 997 417 A1, can be used only on a reel-up which is equipped with a center drive and elements forming a substitute nip.
Furthermore, German patent DE 35 15 519 C2 describes a method in which, although a transfer strip is formed, its connection to the preceding web is already completely broken upstream of the nip. However, in the same way as in U.S. Pat. No. 4,444,362 A, the question also arises here as to how the web start “not bonded to anything” can be transported to the nip and led reliably on to the new core.